Magnet core



pressure.

Patented Mar. 22,1932v UNIT D} STATES "1 'r |m'1' orrlcs PHILIP NOBTON ROSEBY, OI LIVEBQOOL, -E NGLA.ND, ASSIQNOR 'I'O AUTOMATIC TELE- PHONE- MANUFACTURING COMPANY LIKI'IED, OI LIVERPOOL, ENGLAND, A. BRITISH comm IAGNE'I COBB No Drawing: Application and January so, mo, Serial No. mass, and in Grumman mm... a, 1929.

The present invention relates-to the con; struction of magnet cores and is particularly concerned with cores which are made from powdered material by the application of high Such cores find considerable application for loading coils of the type used on telephone lines where their special magnetic properties are 'particularly advantageous.

= t has generally been considered necessary in the manufacture of loading coils of this nature to employ magnetic material in as finely divided a state as; possible in order that the particles may form a compact and substantially homogeneous mass and also so that with the'insulation of individual particles there a may not be 'a conducting path of ap reciable other m aterial,

advantage however, t at after the loading 39 coils have em pressed it is necessary to sub-i ject them to further heat treatment to restore their. magnetic pro rties to the maximum value, or alternative y if such heat treatment is not undertaken loss of magnetic properties of thecoil will necessitate the use of a v coil larger than would otherwise be necessary.

Moreover the heat treatment is liable to afiect adversely the mechanical properties of the pressed core.

, The. hief object of the present invention is the provision of .a method for reducing the magnetic material-to a'suflici'entl fine state without the necessity for first ren ering it brittle. According tothe invention this is'accomplished in that the material is drawn out into wire o f'very small diameter, for in-' stance as small as 4 mils, and is then fed throu h a small hole inja steel plate to a cutter w ich will preferably be of a'rotarly 1 type by which it is cut up}v into very sma lengths. The pieces so produced may then be annealed, coslettised, coated with insulatproportion, say up to 20%, of powdered iron which tends to fill up the interstices and thus produce a more compact core. As an alternative to the use of the coslettising process, a somewhat similar result may be-obtained by treating the chopped up parti cles with phosphorimacid. If hard drawn nickel-iron wire is used the'acid treatment is preferably effected at about 300 F. and results in the production of a deposit of nickel and iron phosphates on each article. The powdered iron for mixing wlth the nickel 11'011 particles is also treated with phosphoric acid ut without heat. The insulating varnish used as a binder preferably comprises a suitable solution of the synthetic resin known under the trade name bakelite. Where the alternative rocess described above is employed it is esirable to use somewhat higher magnetic material prepared as above described are more satisfactory as regards their magnetic properties and after the core has been pressed to the required shape do not need any further treatment to bring these properties back to their original value.

I claim:

1. A magnet core forloadingcoils and the nickel-iron wires treated with phosphoric acid at approximately 300" F. and subset quently sub1ected to high pressure.

3. A process for making magnet cores for use in loading coils and the like in which finely-drawn nickel-iron wire is cut into small lengths, annealed, treated with phosphoric acid and mixed with powdered iron which has been similarly treated with ph'osphoric acid after which the mixture is coated with synthetic resin varnish and then subjected to pressure in a heated mould to cause the particles to agglome'rate.

4. A process as claimed in claim 3 in which the nickel-iron particles are treated with phosphoric acid at approximately 300 F.

while the iron powder is treated with phosphoric acid at ordinary temperatures.

5. A magnet core comprising fourparts of short lengths of nickel-iron wire mixed with one part of powdered iron, a coating of nickel-iron phosphates on said powdered iron and wiresto insulate the same, and insulating material separating said phosphate coated particles and binding the same into a solid mass.

6. A process for making magnet cores which consists in annealing short lengths of nickel-iron wire, treating the same with phos phoric acid and mixing it with powdered iron, then coating the mixture with an insulating compound after which it is subjected late the same and insulating material separating the phosphoric coated powder and wires. I

,In testimony whereof I afiixrmy si ature.

PHILIP NORTON ROS BY.

to heat and pressure to. bind the whole into ,iron wire into small lengths, annealing the Wires, treating them with phosphoric acid at a temperature of 300 F., mixing the treated wires. with powdered iron which has been A l which consists in treating a mixture of powderediron' and short lengths of annealed treated with phosphoric acid, coating the mixture with a binder of insulating material, and then binding the same into a homogene-- ous mass under heatiand pressure.

9. The method of making magnet cores nickel-ironwire with phosphoric acid to insnlate the particles from each other, then coating theparticles with an insulating 'material, and then subjecting the mass to heat and pressure to bind the same into a solid mass. 7

t 10. .A ,inagiiet, core composed of short lengths of nickel-iron wire mixed with pow dered iron, a coating of phosphoric acid on said wires and'said powdered iron to insuiao 

